This plugin is an extension of vim-lsp plugin that supports some additional methods provided by cquery. For now, this methods are $cquery/base, $cquery/derived and $cquery/vars. More methods will be added in future.

Use your plugin manager of choise. For example if you use vim-plug add the following lines to your vimrc:

" First install vim-lsp, this plugin relies on it:
Plug 'prabirshrestha/async.vim'
Plug 'prabirshrestha/vim-lsp'
Plug 'pdavydov108/vim-lsp-cquery'

Now follow the guide how to install cquery and add it to vim-lsp here.

In addition to those commands defined by vim-lsp plugin, this one defines the following additional commands:

1. LspCqueryDerived - when used on function, get a list of functions that override this one. When used on a class, get a list of classes that inherit from this one.
2. LspCqueryBase - get a base class (or a list of base classes) of this class.
3. LspCqueryVars - get a list of all variables that are instances of this user-defined type.
4. LspCqueryCallers - get a list of all callers of this function.

No mappings are defined by default. However, it is trivial to define your own. For example like so:

autocmd FileType c,cc,cpp,cxx,h,hpp nnoremap <leader>fv :LspCqueryDerived<CR>
autocmd FileType c,cc,cpp,cxx,h,hpp nnoremap <leader>fc :LspCqueryCallers<CR>
autocmd FileType c,cc,cpp,cxx,h,hpp nnoremap <leader>fb :LspCqueryBase<CR>
autocmd FileType c,cc,cpp,cxx,h,hpp nnoremap <leader>fi :LspCqueryVars<CR>

For the explanation, see cquery FAQ.